This extends poppler and Okular to support "Next" values of Action Dictionaries as described in Section 8.5.1 of Adobe's PDF 1.7 reference.

The patches build on the differentials from T8274 and are required to make the visibilitytest.pdf from there work properly. (Well except for the Radios ;-) )
There is no functional dependency to T8274 but I've developed them in the same context and I'm using the same test here.

The patches mostly consist of plumbing to carry a list of "Next Actions" through the stack.